In the study, which appears in the online issue of Obstetrics & Gynecology, researchers analyzed the medical records over a decade of more than 22,000 Northern California women who belonged to the same health plan. They looked at how many pounds a woman gained or lost between a first and second pregnancy, in normal weight and overweight women.

To find out whether interpregnancy weight changes affect a woman's risk for gestational diabetes, researchers used a measure called body mass index (BMI) units. (One BMI unit was about 6 pounds based on the average 5-feet 4-inches height of study participants.)

Scientists found that women who had gestational diabetes in their first pregnancy but not during their second gained the fewest BMI units. Women who did not have gestational diabetes in their first pregnancy but developed it in their second gained the most BMI units.

Gestational diabetes occurs when a pregnant woman develops elevated blood sugar levels. Higher-than-normal glucose levels during pregnancy can increase a woman's odds of having a larger baby and a more complicated delivery, and it also puts her and her child at greater risk of having type 2 diabetes later in life.

Gestational diabetes affects 2% to 10% of all pregnancies, according to the American Diabetes Association. Women who are overweight or obese before having a baby are at a greater risk for gestational diabetes.

Preventing Gestational Diabetes

This study revealed that new mothers who put on 12 to 17 pounds between their first and second pregnancy more than double their risk for gestational diabetes compared to women whose weight changed very little. Women who gained 18 pounds or more between births more than triple their chances of developing the condition.

Although gaining weight between pregnancies was shown to increase gestational diabetes risk, this study is the first to explore whether losing weight before expecting a second child could prevent it from recurring.

Weight loss was associated with a lower risk of gestational diabetes primarily among women who were overweight or obese in their first pregnancy, study researcher Samantha Ehrlich, MPH, a project manager at the Kaiser Permanente Division of Research in Oakland, Calif., says in a news release.

"The results support the avoidance of gestational weight retention and postpartum weight gain to decrease the risk of gestational diabetes in a second pregnancy as well as the promotion of postpartum weight loss in overweight or obese women, particularly those with a history of gestational diabetes," Ehrlich says.